The current understanding of neuronal exocytosis is largely based on studies done using model cell systems. Recent developments in the molecular labeling of dopaminergic neurons and microelectrode design allow single neuronal cell electroanalytical studies of dopamine release. In the proposed work, fast scan cyclic voltammetry, constant potential amperometry, and fluorescence imaging will be implemented to measure dopamine exocytosis under various conditions that affect the vesicular storage mechanisms. The frequency and amplitude of release will be monitored during the pharmacological inhibition of membrane transport machinery that regulates the entry and exit of molecules into and from the synaptic vesicle. In order to probe the role of the intravesicular matrix, weak bases will be introduced to disrupt equilibrium conditions. Manipulation of the osmolarity, pH, and temperature of the extracellular fluid will illuminate the role of solution gradients in exocytosis efficiency. This work will then extend to intact neurons from long-term culture. In effort to investigate the classical model of exocytosis, neurotransmitter release will be measured at both the cell body and synaptic terminals of neurons with intact dendrites and axons.